Researchers create tsunami on a chip

By Tereza Pultarova

Published Monday, March 9, 2015

An international team of researchers has developed an innovative nano-optical chip that could be used for generation of nanoscale rogue waves, possibly paving the way for harnessing the power of tsunami.

The study, a collaboration of scientists and engineers from the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia and the UK’s University of St Andrews, was recently published in the Nature Physics journal.

“Our idea was something never tested before,” said Andrea Fratalocchi, assistant professor in Computer, Electrical and Mathematical Science at KAUST, who led the research. “We wanted to demonstrate that small perturbations of a chaotic sea of interacting waves could, contrary to intuition, control the formation of rare events of exceptional amplitude.”

First, Fratalocchi’s team developed new theoretical ideas to explain the formation of rare energetic natural events such as rogue waves - large surface waves that develop spontaneously in deep water and represent a potential risk for vessels and open-ocean oil platforms.

Subsequently, the theory was verified using a planar photonic crystal chip, made by University of St Andrews researchers. During the tests, carried out at the FOM institute AMOLF in the Amsterdam Science Park, the researchers managed to generate ultrafast (163 fs long) and subwavelength (203 nm wide) nanoscale rogue waves.

“By realizing a sea of interacting waves on a photonic chip, we were able to study the formation of rare high energy events in a controlled environment,” said Thomas F Krauss, head of the Photonics Group and Nanocentre Cleanroom at the University of York, the UK, who participated in the development of the experiment and the analysis of data.

“We noted that these events only happened when some sets of waves were missing, which is one of the key insights of our study.”

The researchers were able to visualise behaviour of the nanoscale waves using a specially developed microscope.

“Unlike conventional wave behaviour, it was remarkable to see the rogue waves suddenly appear, seemingly out of nowhere, and then disappear again,” said Kobus Kuipers, head of nanophotonics at FOM institute AMOLF. “As if they had never been there.”

According to Andrea Di Falco, leader of the Synthetic Optics group at the University of St. Andrews, using light confined in an optical chip allows the researchers to control the dissipation of the energy in such a chaotic system.

“It is as if we were able to produce a determined amount of waves of unusual height in a small lake, just by accurately landscaping its coasts and controlling the size and number of its emissaries,” he said.

The team believes the research will in the future lead to technological innovation in the energy research, high speed communication and disaster preparedness.